StackOverflow limits you to five tags per question (answers aren't tagged), and all five are stored in this field. For example, for question 305223, the Tags field is "<offtopic><fun><not-programming-related><jon-skeet>" [...] StackOverflow allows periods in the tag, like the .NET tag and ASP.NET tag. However, in the database, these are stored as "aspûnet". Just something to be aware of.

Hmmm, wondering if the û is not some encoding problem with that very website? It also has an issue with space in "Stack Overflow". ;-)
–
ArjanDec 23 '10 at 14:36

Perhaps this question should be migrated to SO? It's really a programming question that the subject matter of which is related to SO; but it can be for any other app.
–
MohamadDec 23 '10 at 14:48

(@Mel, there's no migration path from MSO to other sites.)
–
ArjanDec 23 '10 at 14:56

@Arjan: a '.' is encoded the same way in virtually all encodings in the world, so no.
–
Andreas BoniniDec 23 '10 at 20:52

@Kop, I was thinking about the dot being replaced by some other character or sequence, that somehow erroneously displayed as û on the site. Like a Unicode û is 0xC3BB in UTF-8. Hence, if the dot would have been encoded as 8-bit ASCII Ã» then erroneously assuming UTF-8 would get one to see the û. Of course, encoding the dot as 8-bit ASCII Ã» makes no sense at all, but there's many other options, especially when there's multiple erroneous encodings/decodings. Anyway, the dot does not seem to be encoded at all. Or: not anymore?
–
ArjanDec 23 '10 at 21:40

1 Answer
1

And using <...> seems just some random way to ensure one can keep the tags apart using some characters that will not appear in any tag itself? Just guessing though. Also, using a separator rather than both some prefix and suffix, makes queries such as where Tags like '%<.net>%' a bit harder. But then I don't know if such ill-performing queries would be used.

Would it not make sense to use a coma delimited list to separate the tags?
–
MohamadDec 23 '10 at 14:58

I guess one might not have expected a dot or hash in the tags either, when designing the database. Hence: can one be sure the comma is never used in a future tag? (Just guessing.)
–
ArjanDec 23 '10 at 14:59

Also, a delimiter is harder in like queries. See my edit, @Mel.
–
ArjanDec 23 '10 at 15:22

I believe the tags field is full-text indexed.
–
Jon SeigelDec 23 '10 at 18:25